What is to be done to those that commit crime? Do not crimes such as rape and murder dictate punishment?
First, I want to be explicit about what I mean by "punishment": I mean the intentional infliction of suffering on a human being for its own sake, either in retribution or in the belief that the suffering itself will have some salutary effect. I do not mean suffering inflicted as an accidental or ancillary effect of some other purpose, even if foreseeable. Thus, the pain and suffering a child experiences from having a vaccination does not count as "punishment"; if someone were to have a virulent communicable disease, quarantining her — entailing suffering from loss of liberty — would not constitute punishment.
We can, without actually punishing people per the above definition, respond to crimes (ignoring for the moment what constitutes a "crime") in two ways. First, we must ensure that on average "crime does not pay": We may legitimately, I think, demand that criminals bear the cost of their crimes, and assign to criminals who are caught recompense for those criminals not caught. Second, we may legitimately take reasonable steps to ensure the criminal does not If a person were to steal, he would responsible for not only what he himself stole, but for a portion of what uncaught thieves also stole.
A person who has committed a crime has proven that he will not voluntarily honor the social contract, explicit or implicit; We cannot trust his protestations that he will in the future change his ways. We must, I think, restrict his liberty in such ways that it becomes impractical to commit future crimes.
It is important to note that in today's society, imprisonment imposes considerably more suffering than is necessary to simply restrict a prisoner's liberty and ability to commit further crimes.